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Thread: Circuit diagram needed for Durst power supplies EST 301 and EST 450

  1. #11
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: Circuit diagram needed for Durst power supplies EST 301 and EST 450

    Quote Originally Posted by ic-racer View Post
    In fact I'm hard pressed to think of any condenser enlarger that came with a regulated supply. Did you have something in mind?
    I was thinking of real enlargers, not 1940's omegas with 212 photo bulbs. (I used one in the 1960s... what a pain!)

    I use a two-color Ilford Multigrade head, which has a separate 300w halogen lamp for each color. Each lamp has its own regulated supply, to maintain the ratio of colors to the VC grade set on the head, and normalize the intensity.

    All tri-color (CMY) heads that I've seen use regulated supplies. I've never used one of these.
    I did use an additive tri-color head when I was printing Cibachromes ~25 years ago.

    There were some early photobulb enlargers that used a Sorensen constant-voltage transformer in a box. To a casual observer it might look like a simple transformer. It did a good job of providing regulated power over a wide range of input voltages.

    As with any other step in the photographic process, powering the enlarger lamp(s) is one factor that can affect final product quality.

    I do have some experience with power supplies, having repaired many, and designed and currently manufacture one.

    - Leigh
    Last edited by Leigh; 3-May-2012 at 14:45.
    If you believe you can, or you believe you can't... you're right.

  2. #12

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    Re: Circuit diagram needed for Durst power supplies EST 301 and EST 450

    Meanwhile I substituted the capacitors in the EST 450 board, but something is still wrong, there's a resistor driving the colector of one transistor that literally burns. I will try to fix the problem (quite hard without the schematics). If I manage to track these problems I will post the solution. Anyway, I'm attaching pictures of the EST450 and EST301 regulator boards in case it's useful for someone else:

    EST 450:
    Click image for larger version. 

Name:	EST_450.jpg 
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ID:	73170

    EST 301:
    Click image for larger version. 

Name:	EST_301.jpg 
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Size:	60.1 KB 
ID:	73171

  3. #13

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    Re: Circuit diagram needed for Durst power supplies EST 301 and EST 450

    Quote Originally Posted by jvelez View Post
    Meanwhile I substituted the capacitors in the EST 450 board, but something is still wrong, there's a resistor driving the colector of one transistor that literally burns. I will try to fix the problem (quite hard without the schematics). If I manage to track these problems I will post the solution. Anyway, I'm attaching pictures of the EST450 and EST301 regulator boards in case it's useful for someone else:

    EST 450:
    Click image for larger version. 

Name:	EST_450.jpg 
Views:	63 
Size:	58.7 KB 
ID:	73170

    Check that transistor. Check the base circuit of that transistor for correct bias.
    EST 301:
    Click image for larger version. 

Name:	EST_301.jpg 
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ID:	73171
    One man's Mede is another man's Persian.

  4. #14

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    Re: Circuit diagram needed for Durst power supplies EST 301 and EST 450

    Hello everybody! Has anyone had any success repairing EST 301 power supply? I replaced three electrolytic capacitors and two burnt-out power resistors R45 and R46 with new ones, but the device didn't work any better. Maybe since the last discussion someone has a copy of the electronic circuit of this power supply unit?
    Click image for larger version. 

Name:	EST 301 control_.jpg 
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ID:	214514

  5. #15
    Paul Ron's Avatar
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    Re: Circuit diagram needed for Durst power supplies EST 301 and EST 450

    is that a rectifier by those resistors? id suspect that part is overloading the resistors.

  6. #16

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    Re: Circuit diagram needed for Durst power supplies EST 301 and EST 450

    Paul Ron,
    it is difficult to determine the cause of such a load on these resistors without the circuit.

  7. #17

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    Re: Circuit diagram needed for Durst power supplies EST 301 and EST 450

    Post a clear detailed photo of the underside of the pcb showing the tracks, and I may be able to trace out a schematic. Missing values can possibly be inferred or calculated based on the surrounding circuit. At any rate it can give an idea of the topology used.

    I'm especially wondering about the function of R47 in the circuit: it appears to be a light dependent resistor (aka, vactrol), which is why it's mounted to that white box, and those can absolutely drift off-value with age (I have seen it many times). Also a chance whatever light source is modulating it may be dead?

    Personally, I'd replace the enlarger's light source with an LED and ditch this ancient power-wasting technology.

  8. #18

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    Re: Circuit diagram needed for Durst power supplies EST 301 and EST 450

    A larger photo of the top would be needed, too. I honestly can't read values on it at the size it is.

  9. #19
    ic-racer's Avatar
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    Re: Circuit diagram needed for Durst power supplies EST 301 and EST 450

    The ceramic resistor looks like it was getting pretty hot. Is the board up-side-down?

  10. #20

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    Re: Circuit diagram needed for Durst power supplies EST 301 and EST 450

    I will take additional photos today or tomorrow. But it seems that in general, everyone is right and it is better to switch to a modern solution with LEDs or replace the 120v/300w lamps in the color head with 24v/250w ones and choose a new switching power supply.

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